A wolf in dog's clothing?

Displaying distinct coat color phenotypes, these two wolf pups from Yellowstone National Park's Agate Creek pack were born in the same litter resulting from the pairing of a black female with a gray male.

In our fairy tales and horror movies, the biggest, baddest, most wolfish wolves, tend to be depicted with black or dark fur. The better to scare us with! But, dark coats are actually a pretty new thing for wolves, according to a new study.

Wolf pups howling.

Scientists have learned that wolves and coyotes acquired the gene responsible for dark coats relatively recently, and that they probably got it by mating with domestic dogs.

Dark coat color is actually relatively rare in wolves and coyotes, though it's unusually common in the wolves of Yellowstone. Researchers recently identified the genetic mutation responsible for dark coat color in domestic dogs, and Tovi Anderson of Stanford University and colleagues now show that this mutation has the same effect in wolves and coyotes.

The researchers also compared the DNA "letters" of this gene in a variety of individual wolves, coyotes and dogs. Based on small differences in the DNA sequence, the researchers determined that the mutation originally occurred in dogs and later spread into wolves and coyotes.

Wolves living on the tundra tend to be light-colored and dark coats are more common among wolves living in the forest. Available tundra habitat is decreasing, so the introduction of a gene from domesticated animals (which is often considered harmful to wildlife) may in this case be helping wolves to adapt and survive.

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This research will be published online by the journal Science, at the Science Express website, on 5 February 2009.